Such pitching machine is described in Patent Document 1 denoted below. According to this document, the ball throwing machine comprises a support body mountable on the ground, a pair of rotary shafts supported by said support body so that they are rotatable around their own parallel axes, a pair of rotary wheels fixed on said rotary shafts concentrically with the latter and juxtaposed radially of said rotary shafts, an electric motor supported by said support body to enable said two rotary wheels to be driven for rotation, and an operatively connecting means for operatively connecting said two rotary wheels to said electric motor. Further, said support body comprises a support body main body which is a carriage mountable on the ground, and a support box body supported on the upper surface of said support body main body and made of metal plate in box form to support said rotary shafts and to receive said operatively connecting means.
When it is desired to make said ball throwing machine perform ball throwing action, said electric motor is driven. Thereupon, said two rotary wheels are rotated in opposite directions in operative association with the driving of the electric motor and through said operatively connecting means and said rotary shafts. And, a ball is fed between the outer peripheral surfaces of said two rotary wheels. Thereupon, said ball is nipped between the outer peripheral surfaces and accelerated and thrown outward.
Patent Document 1: Japanese Paten Laid-Open No. 2001-218883.